In systems for tapping kegs of fluid and particularly containers of beer there has been used a valve assembly secured to the top of the keg for providing access to the fluid ultimately to be delivered from the keg to a remote position for distribution. Typically, the valve assembly includes a dual valve arrangement with a siphon tube which extends from the valve assembly to the bottom of the keg. The valve assembly is fixed within the keg neck or other valve receiving member to provide a valved system, when tapped by a coupler or some other keg tapping means connected to a pressure source, allows pressurized gas to flow into the keg until the desired pressure within the keg is achieved to force the fluid out of the keg through the valve system and ultimately to a distribution device where the fluid can be used to fill glasses and the like. The valve system is one which allows the pressurized gas, usually carbon dioxide, to be forced into the keg but only allows the fluid to be forced out of the keg to distribution device until the keg is extirely emptied of fluid.
The valve assembly includes a body portion which carries an O-ring in sealing engagement with the keg neck to prevent leakage along the interface between the valve body and the neck. To achieve the seal, the O-ring is maintained in a deformed disposition between two metal shoulders of the valve body portion and the keg neck. In many prior art devices, metal shoulders are moved toward each other to compress the O-ring seal by a threaded fitting threadedly engaged with the keg neck. As the threaded fitting is turned down, the shoulders rotate relative to each other and simultaneously move downwardly lineally to deform the O-ring between the valve body and the keg neck. The more the fitting is rotated, the more lineal thrust is imparted to the O-ring deforming it even further.
The problem with this approach is that there is no effective way to limit the compression imparted to the sealing ring. Without such a limitation the sealing ring can be over compressed where it will be subjected to "compression set" in which case the seal will not return substantially to its uncompressed state when the lineal thrust is reduced. This detracts from the ability of the O-ring to maintain its sealing characteristics over a long period of time. Also, the sealing ring may be damaged by action of the shoulders rotating against the surface of the seal thereby negating its sealing properties.
Besides the loss in the efficacy of the seal due to overcompression or damage caused by the rotation by two metal parts, the threads can be loosened after continued use allowing the seal to be violated inadvertently. In addition, a rotation movement is usually employed in attaching a tapping member or a coupler to the valving system. Where threaded fittings are used it is quite easy for the turning of the tapping devices to also rotate the threaded fittings thereby unscrewing one fitting relative to the other moving it lineally away from the O-ring allowing the seal to be violated.
Some prior art valve assemblies used with kegs have included a dual valve system having two valve members each biased into engagement with its respective valve seat. To bias at least one of the valve members, a helical spring circumscribing the siphon tube is utilized. A spring retaining cup is used to hold the helical spring in place with sufficient compression to maintain the valve in a normally closed position. The cup extends downwardly from the valve body about the helical spring and has a radially projecting surface extending inwardly toward the siphon tube to support the bottom of the spring. By having the helical spring disposed in this manner, it becomes difficult to clean allowing residue to build up in the spring coils. Because the cleaning fluids are injected under pressure through the valves, the location of the helical spring adjacent the siphon tube is one which is not readily accessible to the path taken by pressurized cleaning fluid. In addition, by being enclosed by the cup portions, the coils of the spring are not sufficiently exposed to receive the full effect of the cleaning fluid. Where the residue is not completely cleaned away, it can adversely affect the quality of fluid added to the keg for later distribution.
With regard to the coupler or other tapping mechanism, they are inserted by rotation into the valve assembly. Then by separate action, the handle is actuated to open the valves and permit the flow of fluid into and out of the keg in the appropriate channel. After the fluid has been completely dispersed from the keg, the reverse sequence is followed to reseal the valves. If the aforementioned sequence is followed, there will be no loss of fluid or gas in the tapping or untapping procedure.
However, if the handle is inadvertently placed in the tapped or valve open position prior to attaching the coupler to the valve assembly, the valves will be moved to an open position before the coupler is fully in place allowing some leakage to occur until the coupler rotated sufficiently to seal the interface between the coupler and valve assembly. Similarly, if the handle is not relocated to close the valves prior to untapping, leakage will occur until the coupler is rotated out of the valve assembly to a position where the valves reach their naturally closed position. Particularly where the keg contains toxic or otherwise dangerous fluid, the leakage occurring from failure to follow the correct tapping and untapping procedure consitutes a physical danger to the operator. For example, where the keg contains concentrated agricultural chemicals, such as pesticides, insecticides, fertilizer, etc., leakage of these chemicals through an improper coupling technique can be seriously deleterious to the health of the operator.
One of the most effective systems ever devised to overcome the drawbacks of the prior art is described in U.S. Pat. Nos. 4,159,102 and 4,181,143. Broadly stated the systems described in these patents provided better sealability between movable parts to prevent unnecessary leakage, safer operability to protect the operator even from his own errors, and constructional features facilitating cleaning operations and economic savings in manufacturing and assembly, among others.
With regard to the sealing features, the inventions described in the aforementioned patents relate to imparting lineal thrust against a deformable sealing member between two surfaces substantially without relying on rotation. This allows better tolerances to maintain the seal over long periods of time and to avoid inadvertent violation of the seal due to operation of the valve system in tapping and untapping procedures. In addition, the systems are easy to install and provide substantial safety advantages over the systems which have characterized the keg tapping systems of the past.
However, the systems described in U.S. Pat. Nos. 4,159,102 and 4,181,143 exhibit certain drawbacks. For example, the devices of these patents include anti-rotational or locking lugs which act as a time delay mechanism to preclude releasing of the coupler from the keg neck while pressure remains within the vessel. It has been found through usage that, because of the particular location of the counter rotational lugs on these devices it is possible for an operator to unwittingly, or intentionally to attack the locking lugs with a chisel, screwdriver or the like so as to deform or dislodge one or both of the lugs and at the same time damage the adjacent key which forms a critical aspect of the safety time delay feature of the devices. In the devices of the present invention a second key has been added and the locking lugs have been relocated 90 degrees from the keys so that the keys are no longer accessible to the unwitting, or even the intentional, cause of damage or sabotage. This relocation of the locking lugs adds substantially to the inherent safety of the time delay mechanism technique suggested in the aforementioned patents.
The addition of the second key also substantially enhances the overall safety of the system due to the fact that when the valve assemblies are installed with an automatic pressure device, a single lug can be deformed or sheared during the installation process. By doubling the number of safety keys, the shearing forces required during installation to cause or create an unsafe circumstance are effectively doubled. Such a vast increase in the available thrust force from an installation tool is not within the installers adjustment range thereby making damage to the safety keys highly unlikely.
Another drawback to the devices of the previously identified patents resides in the construction of the valve insert which was encapsulated in the first valve member of the dual valve system. This valve insert being a stamped insert of uniform wall thickness, fails to provide the required system safety in the event of fire and other castastrophic events. For example, where the system is exposed to high temperatures such as a building fire or the like, the rubber coating surrounding the valve insert will degrade while at the same time excessive internal steam pressures are building up on the keg tending to force the thin walled stamped valve liner or insert to extrude itself through the heavy walled fixed diameter opening in the keg neck. This, of course, creates an extremely hazardous situation. In the improved system disclosed herein the valve insert is reconfigured and the wall thickness thereof has been selectively increased to the point where it will withstand internal pressures in excess of 4000 psi and temperatures in excess of 3000.degree. before any deformation of the metal-to-metal interfering components can begin. Since fires in beverage dispensing establishments are a reasonably predictable circumstance, this reconfiguration of the valve insert is considered to be a material improvement in the safety aspects of the system and its use.
Still another improvement in the prior art systems resides in the redesign of the spring retainer basket to permit a higher rate of undisturbed flow of fluid, either cleaning fluid or beverages, through the basket. More specifically the spring retainer basket has been redesigned to provide six, rather than four, strategically located fluid flow apertures in the side walls of the basket.